Hydraulic thermostat

ABSTRACT

In the preferred form, a closed tube is provided with fixed shoulders on the opposite sides of a ring-shaped elastic seal member and a washer surrounding and having close fit with a rod extending into a viscous silicone thermal expansion fluid. At the open end of the tube the rod has a shoulder adapted on the inward movement to engage a double throw switch to move it from engagement with an outer contact into engagement with an inner contact. The rod is urged inwardly by a coil spring having its inner end pressing against a spring retainer fixed to the rod and having its outer end pressing against a second seal ring surrounding the rod for preventing leakage into an outer part of the tube.

United States Patent Bright [541 HYDRAULIC THERMOSTAT [72] Inventor: James A. Bright, Dayton, Ohio [73] Assignee: General Motors Corporation, Detroit,

Mich. I

[22] Filed: Jan. 14, 1971' 21 Appl. No.: 106,443

[52] U.S. Cl. ..337/315, 73/3683, 200/153 V,

151' 3,680,022 [451 July 25,1972

Primary Examiner-Bernard A. Gilheany Assistant Examiner-Dewitt M. Morgan Attorney-William S. Pettigrew, Frederick M. Ritchie and Edward P. Barthel [57] ABSTRACT In the preferred form, a closed tube is provided with fixed shoulders on the opposite sides of a ring-shaped elastic seal member and a washer surrounding and having close fit with a rod extending into a viscous silicone thermal expansion fluid. At the open end of the tube the rod has a shoulder adapted on the inward movement to engage a double throw switch to move it from engagement with an outer contact into engagement with an inner contact. The rod is urged inwardly by a coil spring having its inner end pressing against a spring retainer fixed to the rod and having its outer end pressing against a second seal ring surrounding the rod for preventing leakage into an outer part of the tube.

3 Claims, 4 Drawing Figures HYDRAULIC THERMOSTAT This invention relates to a simple hydraulic thermostat having a lost motion connection between the control device and the thermally responsive element which is effective to connect when cooled below a predetermined temperature range. An example of a prior art thermostat of this general type is disclosed in US. Pat. No.'3,529,770 issued Sept. 22, 1970, and assigned to the same assignee as the instant application.

It is an object of this invention to provide a simple, inexpensive and durable low differential hydraulic thermostat having improved sensitivity'which will not leak or lose its accuracy over extended periods at high and/or low temperatures.

Further objects and features of the invention will be readily apparent from the following description, reference being had to the accompanying drawing wherein preferred embodiments of the present invention are clearly shown.

In the drawings:

FIG. 1 is an enlarged transverse sectional view of a hydraulic thermostat embodying one form of my invention;

FIG. 2 is an enlarged fragmentary sectional view of the inner seal ring; and

FIG. 3 is a fragmentary enlarged sectional view of a portion of the outer seal ring;

FIG. 4 is a perspective member.

Referring now to the drawing and more particularly to FIG. 1, there is shown a tube enclosure 20 preferably of brass having closed end 22 and a shoulder 24 separating the smaller diameter portion 26 from a larger diameter portion 28. Within the smaller diameter portion 26 filling the closed end 22 is a viscous thermal expansion fluid 30 which preferably is -a viscous fluoro silicone that may have a viscosity range from about 12,500 'to 2,500,000 centipoise (unit measure of viscosity l/ 100 poise). If it is desired, however, other thermal expansion fluids may be used such as a mineral wax. The tube 20 may be made of brass or any other suitable material.

Extending into the fluid 30 within the tube 20 is an actuator rod assembly 31 comprising a stainless steel rod portion 32, which is conically pointed at its free end, and a suitable electrical insulating plastic rod portion 33 preferably of acetal resin including approximately 20 to 30 percent glass filled polycarbonate. The plastic rod portion has an enlarged coupling socket 34 receiving one end of the steel rod portion 32 which is secured therein by suitable means such as an epoxy cement. Making tight fit within the smaller tube portion 26 are a pair of brass sleeves 35 and 36 which have considerable annular clearance space, indicated at 37 in enlarged FIG. 2, with the steel rod portion 32 to prevent binding between the rod 32 and the sleeves. These sleeves 35 and 36 are spaced to provide opposite shoulders 38 and 39. Between the shoulders 38 and 39 is a brass washer 40 making a close sliding fitwith the outer surface of the steel rod 32 while having considerable clearance with the inside surface or diameter 41 of the wall of the tube portion 26. In addition to the washer 40, sealring 42 of elastic fluorosilicone is located between the shoulders 38 and 39 with seal 42 in juxtaposed relation with the washer 40. It should be noted that while a single torous shaped or O-ring seal 42 is shown two or more O-ring seals could be employed as may be required without departing from the scope of my invention.

The sleeve 35 is first pressed into place after which the seal ring 42 and the washer 40 are inserted after which the outer sleeve 36 is pressed into place until the seal ring 42 and the washer 40 substantially entirely fill the space between the shoulders 38 and 39 and between the steel rod 32 and the inner surface 41 of the tube portion 26. The tube portion 26 is provided with an annular crimp or notch 46 bearing against the outer edges of an annular groove 44 in the sleeve 36 to plan view of the switch plate prevent the expansion of the hydraulic fluid 30 from moving the sleeve 36 away from the closed end 22 of the tube 20. By virtue of this arrangement the seal ring 42 is fixed relative to the inside surface 41 to prevent the seal ring 42 from moving the rod assembly 31 toward the right prematurely during the contraction of the fluid 30 to cause premature opening of contacts to be described.

The coupling socket portion 34 of the actuating rod assembly 31 has molded thereon an annular inner spring retainer 52, located in the larger tube portion 28, which supports the inner end of the coil spring 54 which has a force sufficient to overcome the frictional drag of the seal ring 42 on the rod portion 32 and also to provide the desired contact pressure. This spring may have a force of the order of 1 lb. or less. The outer end of the spring 54 bears against a combined spring retainer and seal cup 56 shown in detail in FIG. 3 and preferably molded from acetal resin having an annular shoulder 57 for centering the spring 54, and on the opposite side a cup-shaped recess 58 receiving the torous shaped seal ring 59 of elastic fluorosilicone which may be identical to the inner seal ring 42. The inner wall of the tube portion 28 is threaded at 50 to receive a threaded hollow projection 60 which surrounds the rod portion 33 and threads into the open end of the tube 20. The threaded projection 60 has a snug threaded fit within the outer end of the larger tube portion 28 and extends from a heavy platform 62 which is integral with the threaded projection 60 and has a coaxial passage 64 in it receiving the rod portion 33 of rod assembly 31 while the seal ring 59 is held tightly against the inner end of the protrusion 60 by the spring 54. The heavy platform 62 contains a passage 63 concentric with the passage 64 having a smaller clearance with the rod portion 33. The platform 62 is preferably made of a suitable electrical insulating plastic material such as polycarbonate.

This platform 62 supports a terminal 66 in the form of an extruded eyelet 67 extending through an aperture in the platform 62, having connected to it one end of an L-shaped switch plate member indicated generally at 68. The switch plate 68,

as seen in FIG. 4, has a circular aperture 61 for reception of eyelet 67 and a slotted aperture 69 in spring blade 71 for reception of the rod portion 33 to allow for the axial movement of the rod 33 through the spring blade 71. Raised blade portion 71 of the switch plate member 68 has a pair of humps 70 formed on opposite sides of the rod aperture 69. The movable spring blade 71 provides a double throw contact portion 72 in its free end which is adapted to be moved between the inner and outer stationary contacts 74 and 76 respectively. The contacts 74 and 76 connect to separate terminals provided on a second platform 78 which is integral with the first platform 62. The inner contact 74 is connected to an eyelet type terminal 80 while the outer contact 76 is connected in a similar manner to a third terminal, now shown.

Thus, the outer end of the insulated plastic rod portion 33 extends through the slotted clearance aperture 69 in the double throw spring blade contact member 71 between the two humps 70 and on its outer end has press fitted thereon a cap 82 of polycarbonate or other electrical insulating material.

having a wide annular inner shoulder 84 located so as to engage the humps 70 when the temperature of the fluid 30 is lowered sufiiciently. The position of the humps 70 relative to the raised spring blade 71 anchorage, indicated at 85, and the contact 72 assures a multiplying or mechanical amplification of the movement of the rod assembly 31 about 3:1.

The temperature of the fluid at which either contact 74 or 76 is contacted is adjusted by turning the platform 62 and the protrusion 60 relative to the tube 20. The humps 70 and the shoulder 84 form a lost motion connection which connects on the inward or contact opening movement of the actuator rod assembly 31 upon sufficient lowering of the temperature of the thermal expansion fluid 30 until the movable contact member 68 is prevented from moving further by the engagement of the blade contact 72 with the inner contact 74. Further contraction of the fluid 30 will merely create a vacuum in the sealed chamber without producing any damage or stress on the parts. Conversely, expansion of the fluid 30 and the outward movement of the rod assembly 31 will not produce any strain or stress on the control since the rod assembly 31 and the cap 82 are free to move outwardly and disconnect the shoulder 84 from the humps 70 to provide the lost motion. The cap 82 can move away from the humps 70 to accommodate any thermal expansion within the highest expected temperatures such as those incurred during shipping. The outer portion of the rod portion 33 and the cap 84 are protected by a third platform 86 provided with an aperture 88 aligned with the rod assembly 31, the cap 82 and the slotted aperture 69.

Since the rod assembly 31 with the exception of coupling socket 34 is of uniform diameter throughout, its movement through the seal rings 42 and 59 will not draw in or expel air or any other fluid from any portion within the tube 20. In the preferred form the plastic and steel portions 32 and 33 of rod assembly 31 have a diameter of the order of 0.070 in. The high viscosity of the fluid 30 minimizes leakage and makes it possible to keep the force of the spring 54 comparatively low. The spring force need only be sufficient to overcome the friction and provide sufficient contact pressure between the contacts 72 and 74.

It is important that no air be trapped in the chamber containing the fluid 30. Any air in this fluid 30 makes the switch slow to respond and causes it to have a large temperature differential between the temperatures at which the spring blade contact 72 breaks contact with the contact 74 and makes contact with the contacts 76 and vice-versa. Preferably the seal ring 42 is compressed sufficiently between the sleeve shoulders 38 and 39 so that it occupies substantially all the space between them surrounding the rod portion 32 within the tube 20. It will be noted that in applicants arrangement the sleeve 35 is dimensioned such that it does not require crimping of the tube 26 to secure the sleeve 35 in place while crimping of sleeve 36 is required because of an increase in dimensional tolerances caused by locating sleeve 35.

The small washer 42 prevents the pressure of the fluid 30 from causing the shearing of the seal ring 42 through the clearance 37 between the rod 32 and the sleeve 36. The inner I diameter clearance 37 of the sleeves 35 and 36 allows for slight axial misalignment of the actuator rod assembly 31 to prevent any interference or binding with the sleeves. The seal 59 prevents the entrance of moisture and other extraneous fluids and solids and also prevents any leakage of the thermal expansion fluid 30 onto the contacts 72, 74 and 76.

While the embodiment of the present invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is:

1. A thermostatic control including an enclosure containing a thermally expansible fluid, an operating rod within the enclosure extending into contact with the fluid and responsive to the expansion of the fluid, a seal member surrounding said rod and having sealing surfaces in sealing contact with said rod and in sealing contact with said enclosure for preventing the escape of said fluid, spring means for urging said rod into contact with said fluid, wherein the improvement comprises providing said enclosure with shoulders on opposite sides of said seal member having a large clearance with said rod so as to insure against close tolerance binding between said rod and said shoulders, and a washer surrounding and having a close sliding fit with said rod and a large clearance within said enclosure fitted between one of said shoulders and said seal member for preventing said seal member from moving with said rod, a control device mounted upon said enclosure having a bias to a first control position in the direction of the outward movement of said rod upon the expansion of said fluid, said rod having a lost motion connection means connecting with and operating said control device from said first control position to a second control position only upon a predetermined,

inward movement of said rod upon contraction of said fluid,

said lost motion connecting means being arranged to disconnect from said control device upon predetermined expansion of said fluid and predetermined outward movement of said rod to prevent damage to the control when subjected to abnormally high temperatures.

2. A thermostatic control including an enclosure containing a thermally expansible fluid, an operating rod within the enclosure having its free end extending into contact with the fluid and responsive to the expansion of the fluid, a seal member surrounding said'rod and having sealing surfaces in sealing contact with said rod and in sealing contact with said enclosure for preventing the escape of said fluid, spring means for urging said rod into contact with said fluid, wherein the improvement comprises providing said enclosure with means rigid with said enclosure supporting opposite sides of said seal member for preventing said seal member from moving with said rod, said enclosure being provided with a platform having a spring blade including contacts thereon supported on said platform, a pair of spaced inner and outer fixed contacts on said platform positioned in double throw fashion with the contacts of said spring blade, said spring blade having an oversize slotted aperture therein aligned with a passage on said platform for reception and axial travel of said rod therethrough, said spring blade having a bias to a first control position in contact with said outer contact in the direction of the outward movement of said rod upon the expansion of said fluid, said rod having engaging means fitted on its outer end for lost motion engagement with said spring blade for connecting with and operating said spring blade to a second control position in contact with said inner fixed contact only upon a predetermined inward movement of said rod upon contraction of said fluid, said engaging means being arranged to disconnect from said spring blade upon predetermined expansion of said fluid and predetermined outward movement of said rod to prevent damage to the control device when subjected to abnormally high temperatures. I

3. A thermostatic control including an enclosure containing a thermally expansible fluid, an operating rod within the enclosure having its free end extending into contact with the fluid and responsive to the expansion of the fluid, a seal member surrounding said rod and having sealing surfaces in sealing contact with said rod and in sealing contact with said enclosure for preventing the escape of said fluid, spring means for urging said rod into contact with said fluid, wherein the improvement comprises a pair of spaced sleeves surrounding said rod on opposite sides of said seal member, said sleeves providing said enclosure with shoulders on opposite sides of said seal member, said sleeves having a large clearance with said rod so as to insure against close tolerance binding between said rod and said sleeves, and a washer surrounding and having a close sliding fit with said rod and a large clearance within said enclosure fitted between one of said sleeve shoulders and said seal member for preventing said seal member from moving with said rod, said seal member substantially filling all the confined space between its adjacent sleeve shoulder and said washer and between adjacent portions of said rod and the interior surfaces of said enclosure, said seal member having an original unconfined shape of a torus and being of a resilient elastic material, said enclosure being provided with a platform having a spring blade including contacts thereon supported on said platform, a pair of spaced inner and outer fixed contacts on said platform positioned in double throw fashion with the contacts of said spring blade, said spring blade having an oversize slotted aperture therein aligned with a passage on said platform for reception and axial travel of said rod therethrough, said spring blade having a bias to a first control position in contact with said outer contact in the direction of the outward movement of said rod upon the expansion of said fluid, said rod having a cap fitted on its outer end for lost motion engagement with said spring blade for connecting with and operating said spring blade to a second control position in contact with said inner fixed contact only upon a predetermined inward movement of said rod upon contraction of said fluid, said cap being arranged to disconnect from said spring blade upon predetermined expansion of said fluid and predetermined outward movement of said rod to prevent damage to the control device when subjected to abnormally high temperatures. 

1. A thermostatic control including an enclosure containing a thermally expansible fluid, an operating rod within the enclosure extending into contact with the fluid and responsive to the expansion of the fluid, a seal member surrounding said rod and having sealing surfaces in sealing contact with said rod and in sealing contact with said enclosure for preventing the escape of said fluid, spring means for urging said rod into contact with said fluid, wherein the improvement comprises providing said enclosure with shoulders on opposite sides of said seal member having a large clearance with said rod so as to insure against close tolerance binding between said rod and said shoulders, and a washer surrounding and having a close sliding fit with said rod and a large clearance within said enclosure fitted between one of said shoulders and said seal member for preventing said seal member from moving with said rod, a control device mounted upon said enclosure having a bias to a first control position in the direction of the outward movement of said rod upon the expansion of said fluid, said rod having a lost motion connection means connecting with and operating said control device from said first control position to a second control position only upon a predetermined inward movement of said rod upon contraction of said fluid, said lost motion connecting means being arranged to disconnect from said control device upon predetermined expansion of said fluid and predetermined outward movement of said rod to prevent damage to the control when subjected to abnormally high temperatures.
 2. A thermostatic control including an enclosure containing a thermally expansible fluid, an operating rod within the enclosure having its free end extending into contact with the fluid and responsive to the expansion of the fluid, a seal member surrounding said rod and having sealing surfaces in sealing contact with said rod and in sealing contact with said enclosure for preventing the escape of said fluid, spring means for urging said rod into contact with said fluid, wherein the improvement comprises providing said enclosure with means rigid with said enclosure supporting opposite sides of said seal member for preventing said seal member from moving with said rod, said enclosure being provided with a platform having a spring blade including contacts thereon supported on said platform, a pair of spaced inner and outer fixed contacts on said platform positioned in double throw fashion with the contacts of said spring blade, said spring blade having an oversize slotted aperture therein aligned with a passage on said platform for reception and axial travel of said rod therethrough, said spring blade having a bias to a first control position in contact with said outer contact in the direction of the outward movement of said rod upon the expansion of said fluid, said rod having engaging means fitted on its outer end for lost motion engagement with said spring blade for connecting with and operating said spring blade to a second control position in contact with said inner fixed contact only upon a predetermined inward movement of said rod upon contraction of said fluid, said engaging means being arranged to disconnect from said spring blade upon predetermined expansion of said fluid and predetermined outward movement of said rod to prevent damage to the control device when subjected to abnormally high temperatures.
 3. A thermostatic control including an enclosure containing a thermally expansible fluid, an operating rod within the enclosure having its frEe end extending into contact with the fluid and responsive to the expansion of the fluid, a seal member surrounding said rod and having sealing surfaces in sealing contact with said rod and in sealing contact with said enclosure for preventing the escape of said fluid, spring means for urging said rod into contact with said fluid, wherein the improvement comprises a pair of spaced sleeves surrounding said rod on opposite sides of said seal member, said sleeves providing said enclosure with shoulders on opposite sides of said seal member, said sleeves having a large clearance with said rod so as to insure against close tolerance binding between said rod and said sleeves, and a washer surrounding and having a close sliding fit with said rod and a large clearance within said enclosure fitted between one of said sleeve shoulders and said seal member for preventing said seal member from moving with said rod, said seal member substantially filling all the confined space between its adjacent sleeve shoulder and said washer and between adjacent portions of said rod and the interior surfaces of said enclosure, said seal member having an original unconfined shape of a torus and being of a resilient elastic material, said enclosure being provided with a platform having a spring blade including contacts thereon supported on said platform, a pair of spaced inner and outer fixed contacts on said platform positioned in double throw fashion with the contacts of said spring blade, said spring blade having an oversize slotted aperture therein aligned with a passage on said platform for reception and axial travel of said rod therethrough, said spring blade having a bias to a first control position in contact with said outer contact in the direction of the outward movement of said rod upon the expansion of said fluid, said rod having a cap fitted on its outer end for lost motion engagement with said spring blade for connecting with and operating said spring blade to a second control position in contact with said inner fixed contact only upon a predetermined inward movement of said rod upon contraction of said fluid, said cap being arranged to disconnect from said spring blade upon predetermined expansion of said fluid and predetermined outward movement of said rod to prevent damage to the control device when subjected to abnormally high temperatures. 